Yeon-Joon Park

Prevalence of metallo-β-lactamase among Pseudomonas aeruginosa and Acinetobacter baumannii in a Korean University hospital and comparison of screening methods for detecting metallo-β-lactamase

To identify the metallo-β-lactamases (MBLs) prevalent in Korea, a total of 130 clinical isolates of Pseudomonas aeruginosa and Acinetobacter baumannii (99 P. aeruginosa and 31 A. baumannii) with a reduced susceptibility to imipenem (IPM) and/or ceftazidime (CAZ) was subjected to PCR analyses with primers specific to blaIMP-1, blaVIM-1, and blaVIM-2. In addition, inhibitor-potentiated disk diffusion methods (IPD) using two kinds of substrate–inhibitor combinations (ceftazidime–2-mercaptopropionic acid (2MPA) and imipenem–EDTA) were investigated. Thirty-three isolates (29 P. aeruginosa and 4 A. baumannii) carried blaVIM-2 and two P. aeruginosa isolates harbored blaIMP-1. The enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) pattern revealed that many of the VIM-2-producing P. aeruginosa isolates were clonally related, whereas the A. baumannii isolates were diverse. The inhibitor-potentiated disk diffusion test using imipenem–EDTA was highly sensitive and specific for detecting the VIM-2 producer. These results suggest that VIM-2 is an important MBL in P. aeruginosa and A. baumannii in the Korean hospital of this study and that the IMP-1-producing P. aeruginosa has also emerged. Screening for MBLs and strict infection control for these isolates will contribute to prevent further spread of resistance.

Procalcitonin as a diagnostic marker and IL-6 as a prognostic marker for sepsis ☆

The diagnosis and prognosis of sepsis after antimicrobial therapy among systemic inflammatory response syndrome (SIRS) patients were evaluated with the biomarkers procalcitonin (PCT), interleukin-6 (IL-6), C-reactive protein (CRP), erythrocyte sedimentation rate, and white blood cell counts. Among 177 consecutive SIRS patients, 78 exhibited sepsis, with Escherichia coli (23.1%) being the most common pathogen. PCT showed the best diagnostic performance, with 74.4% and 93.7% sensitivity and 86.7% and 75.2% specificity among sepsis and severe sepsis/septic shock patients, respectively. PCT, IL-6, and CRP levels were significantly increased in nonsurvivors compared to survivors. Serial measurements at 0, 12, 24, 48, 72, and 96 h showed that IL-6 showed better kinetics in the survivor group and was decreased in more than 86% of survivors by the second day. PCT can support the diagnosis of bacterial infection, especially in septic shock and severe sepsis patients. IL6 exhibited the better kinetics for monitoring the effectiveness of antibiotic treatment.

Molecular analysis of isoniazid resistance in Mycobacterium tuberculosis isolates recovered from South Korea

The katG, inhA and ahpC genes, in 71 isoniazid (INH)-resistant and 26 INH-susceptible Mycobacterium tuberculosis isolates, from South Korea were examined by sequencing and MspI restriction enzyme analysis. Mutations in the katG 315 alone, katG 315 plus inhA, katG 315 plus ahpC, katG 309 alone, katG 309 plus inhA, inhA alone, and ahpC alone, were detected in 54.9, 2.8, 1.4, 1.4, 1.4, 19.7, and 5.6% of the 71 INH-resistant isolates, respectively. There was no statistically significant difference (p > 0.05) in the frequencies of these mutations for the INH-monoresistant compared with the multidrug-resistant isolates. Mutations in the katG codon 315 were associated with the high-level of INH resistance (MIC, >1 microg/ml), whereas the mutation in the inhA promoter region was associated with the low-level of INH resistance (MIC, >0.2 to 1 microg/ml). The previously undescribed GGT-->GAT (Gly-->Asp) mutation in the katG codon 309 was found in two rifampin, including-multidrug-resistant isolates, but we cannot assess if this is predictive of INH resistance. The sensitivity and specificity of molecular analysis of the katG codon 315 and/or the inhA promoter region were 80.3 and 100%, respectively. Therefore, mutations in these regions are highly predictive of INH resistance in South Korea.

Carbapenem-resistant Acinetobacter baumannii: diversity of resistant mechanisms and risk factors for infection.

Carbapenem-resistant Acinetobacter baumannii (CRAB) are an increasing infectious threat in hospitals. We investigated the clinical epidemiology of CRAB infections vs. colonization in patients, and examined the mechanisms of resistance associated with elevated minimum inhibitory concentrations (MICs) for carbapenems. From January to June 2009, 75 CRAB strains were collected. CRAB infection was significantly associated with malignancy and a high APACHE II score. The most dominant resistance mechanism was ISAba1 preceding OXA-51, producing strains with overexpression of efflux pump. Strains carrying blaOXA-23-like enzymes had higher carbapenem MICs than those carrying blaOXA-51-like enzymes; however, the presence of multiple mechanisms did not result in increased resistance to carbapenems. There was no difference in the resistance mechanisms in strains from infected and colonized patients. The majority of strains were genetically diverse by DNA macrorestriction although there was evidence of clonal spread of four clusters of strains in patients.

Rates of fecal transmission of extended-spectrum β-lactamase-producing and carbapenem-resistant Enterobacteriaceae among patients in intensive care units in Korea.

Background We investigated the rates of fecal transmission of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae (ESBL-E) and carbapenem-resistant Enterobacteriaceae (CRE) among patients admitted to intensive care units (ICUs). Methods From June to August 2012, rectal cultures were acquired from all patients at ICU admission. For patients not carrying ESBL-E or CRE at admission, follow-up cultures were performed to detect acquisition. A chromogenic assay was used to screen for ESBL-E and CRE. Bacterial species identification and antibiotic susceptibility tests were performed using the Vitek 2 system (bioMérieux, France). ESBL genotypes were determined by PCR, and clonal relatedness of the isolates was assessed by pulsed-field gel electrophoresis. Results Out of 347 ICU admissions, 98 patients were found to be carriers of ESBL-E (28.2%, 98/347). Follow-up cultures were acquired from 91 of the patients who tested negative for ESBL-E at admission; the acquisition rate in this group was 12.1% (11/91), although none was a nosocomial transmission. For CRE, the prevalence of fecal carriage was 0.3% (1/347), and the acquisition rate was 2.9% (4/140). None of the CRE isolates were carbapenemase-producers. Conclusions The high prevalence of ESBL-E carriage on admission (28.2%), coupled with rare nosocomial transmission and the very low carriage rate of CRE (0.3%), challenge the routine use of active surveillance in non-epidemic settings. Nevertheless, passive surveillance measures, such as rapid and accurate screening of clinical specimens, will be critical for controlling the spread of CRE.

Impact of vancomycin resistance on mortality in neutropenic patients with enterococcal bloodstream infection: a retrospective study

BackgroundVancomycin-resistant Enterococcus (VRE) bloodstream infection (BSI) is generally associated with the delayed administration of adequate antibiotics. The identification of risk factors and outcomes of VRE BSI is necessary for establishing strategies for managing neutropenic fever in patients with hematological malignancies.MethodsWe retrospectively analysed consecutive cases of enterococcal BSI in patients with neutropenia after chemotherapy or stem cell transplantation between July 2009 and December 2011 at a single center.ResultsDuring the 30-month period, among 1,587 neutropenic patients, the incidence rate of enterococcal BSI was 1.76 cases per 1,000 person-days. Of the 91 enterococcal BSIs, there were 24 cases of VRE. VRE BSI was associated with E. faecium infection (P < .001), prolonged hospitalization (P = .025) and delayed administration (≥48 hours after the febrile episode) of adequate antibiotics (P = .002). The attributable mortality was 17% and 9% for VRE and vancomycin-susceptible Enterococcus (VSE), respectively (P = .447). The 30-day crude mortality was 27% and 23% for VRE and VSE, respectively (OR 1.38, 95% CI 0.53–3.59; P = .059). Only SAPS-II was an independent predictive factor for death (adjusted OR 1.12, 95% CI 1.08–1.17; P < .001).ConclusionsIn conclusion, vancomycin resistance showed some trend towards increasing 30-day mortality, but is not statistically significant despite the delayed use of adequate antibiotics (≥48 hours). Only underlying severity of medical condition predicts poor outcome in a relatively homogeneous group of neutropenic patients.

Vancomycin-Tolerant Streptococcus pneumoniae in Korea

ABSTRACT A nationwide surveillance study was undertaken to monitor antimicrobial resistance among clinical isolates of Streptococcus pneumoniae in Korea, with a special focus on vancomycin tolerance. For the 6-month period from March to August 2002, clinical isolates of S. pneumoniae were collected from 11 university hospitals and 1 reference laboratory. One-hundred eighty-eight isolates were measured for lysis rates after exposure to vancomycin for 4 h. Two vancomycin-tolerant S. pneumoniae (VTSP) strains, S3 and H8, were isolated from sputum cultures of two patients, who had stayed in intensive-care units of different hospitals with long-term antibiotic therapy and were not treated for pneumococcal pneumonia. The penicillin, cefotaxime, and vancomycin MICs for S3 were 8 μg/ml, >16 μg/ml, and 0.5 μg/ml, and those for H8 were 2 μg/ml, 2 μg/ml, and 0.5 μg/ml, respectively. While S3 belonged to serotype 23F and was autolysin defective, H8 belonged to serotype 13F and had intact autolysin. These strains were not clonally related as determined by pulsed-field gel electrophoresis of chromosomal DNA. In agreement with previous reports, both isolates showed pairing of TIGR4 vex2 with R6 pep27 and had two identical amino acid substitutions, Q441K in vncS and N25D in vex2. These findings indicate that two VTSP strains have emerged independently in Korea, suggesting a prevalence rate of 1.1%. The emergence of VTSP would be a serious threat in Korea, where there are significant rates of penicillin resistance in S. pneumoniae. Monitoring of the prevalence of VTSP and further investigation of the clinical relevance of VTSP are warranted.

Antimicrobial Susceptibility of Stenotrophomonas maltophilia Isolates from Korea, and the Activity of Antimicrobial Combinations against the Isolates

The aim of this study was to determine antimicrobial susceptibility of recent clinical Stenotrophomonas maltophilia isolates from Korea, and to compare the activity levels of several combinations of antimicrobials. A total of 206 non-duplicate clinical isolates of S. maltophilia was collected in 2010 from 11 university hospitals. Antimicrobial susceptibility testing was performed using the Clinical Laboratory Standards Institute agar dilution method. In vitro activity of antimicrobial combinations was tested using the checkerboard method. The susceptibility rates to trimethoprim-sulfamethoxazole and minocycline were 96% and 99%, respectively. The susceptibility rate to levofloxacin was 64%. All of four antimicrobial combinations showed synergy against many S. maltophilia isolates. A combination of trimethoprim-sulfamethoxazole plus ticarcillin-clavulanate was most synergistic among the combinations. None of the combinations showed antagonistic activity. Therefore, some of the combinations may be more useful than individual drugs in the treatment of S. maltophilia infection. Further clinical studies are warranted to validate our in vitro test results.

Comparative evaluation of ELISA and Luminex panel reactive antibody assays for HLA alloantibody screening

BACKGROUND For the detection of HLA antibodies, solid-phase tests using purified HLA antigens are increasingly used. In this study, we analyzed the panel reactive antibody (PRA) test results using ELISA and Luminex methods, and the results were compared with those of crossmatch test. METHODS A total of 111 sera including 90 sera from kidney transplanted patients were tested. ELISA-PRA was performed using Lambda Antigen Tray Class I and II Mixed kits (One Lambda Inc., USA) and additional test was performed to identify HLA specificities. Luminex-PRA tests were performed using LABScreen Mixed kits (One Lambda Inc., USA) and LIFECODES LifeScreen Deluxe kits (Tepnel Co., USA). RESULTS The positive rates of PRA were higher in Tepnel (P=0.006) and One Lambda Luminex (P<0.001) methods than ELISA, without significant difference between two Luminex methods (P=0.087). The overall concordance rate among the three PRA tests was 62.2% (69/111). The positive and negative predictive values of PRA tests for the flow cytometric crossmatch were 33.3-45.7% and 85.7-89.5%, respectively. Of the two Luminex methods, One Lambda showed higher positive rate than Tepnel for the detection of class I antibodies. The sensitivity of pretransplant PRA for the detection of posttransplant acute rejection episodes was higher in Luminex (P=0.007 for Tepnel, P=0.003 for One lambda) than ELISA method. CONCLUSIONS Different methods used to detect HLA antibodies showed discrepant results. As the Luminex method was more sensitive than ELISA for the detection of HLA antibodies, it can be used as a routine test in the transplantation laboratory.

Comparative study of immunofluorescent antinuclear antibody test and line immunoassay detecting 15 specific autoantibodies in patients with systemic rheumatic disease.

Based on the currently proposed algorithms, antibodies specificities (sp‐ANAs) are identified mainly in samples positive for fluorescent antinuclear antibodies (FANA) screening tests. The purpose of the present study was to compare diagnostic performances of FANA and line immune assay (LIA) detecting 15 sp‐ANAs in patients with systemic rheumatic diseases (SRD). In 948 sera from the patients with SRD (n = 590) and non‐SRD (n = 358), we evaluated the fluorescent patterns and intensities in the FANA test, and compared the FANA results with sp‐ANAs against nRNP, Sm, SS‐A, Ro52, SS‐B, Scl‐70, PM/Scl, Jo‐1, CENP B, PCNA, dsDNA, nucleosome, histone, ribosomal‐P, and M2. The sensitivity and specificity was 75.9% and 52.5% of FANA test and 62.0% and 84.4% of sp‐ANAs test for SRD detection. The overall agreement between FANA and sp‐ANAs results was 69.2% (Kappa coefficient; 0.404). According to the clinical diagnosis, the levels of agreement varied from 33.3% to 83.1%. The positive predictive values of each FANA pattern for the detection of sp‐ANAs were less than 50% except for the discrete speckled pattern (91.7%). The 1:100 intensity of FANA as well as the monoreactivity of LIA, anti‐SSA(−)/anti‐Ro52(+), or FANA(−)/sp‐ANAs(+) was associated with non‐SRD. Antibodies against ribosomal‐P or PCNA were specific for systemic lupus eryhthematosus. This study highlights the need for careful interpretation of FANA test results to assess sp‐ANAs and the application of sp‐ANAs tests including less‐common autoantibodies. In patients with clinical suspicion of SRD, screening with both FANA and sp‐ANAs tests could improve diagnostic efficiency. J. Clin. Lab. Anal. 26:307‐314, 2012.